Monoclonal antibodies are becoming powerful therapeutic agents in the treatment of a number of diseases and conditions, including but not limited to cancer, respiratory diseases, inflammatory diseases, and infectious diseases. Generally, therapies that include antibodies require the delivery of between 100 mg and 1 g of antibody per dose. A commonly used approach for such treatments is to use intravenous infusions of from about 2 to 20 mL of a 50 mg/mL solution of the antibody. Because introduction methods other than intravenous administration, such as subcutaneous injection, are desired, it would be advantageous to have more concentrated solutions of the antibodies. However, concentrated solutions of antibodies can lead to problems, including but not limited to, highly viscous solutions, protein aggregation, and problems with the stability of the solutions.
Fragments of antibodies have been crystallized, for example, for use in X ray crystallography. Previously reported methods of crystallizing monoclonal antibodies have generally used the vapor diffusion technique. Drawbacks of this technique include the minute quantities of crystals that are produced, and the use of agents that in some cases are unacceptable for use in humans. Batch-process methods can also be used to produce slightly larger quantities of crystals. Commonly used batch-process methods typically utilize organic or polymeric precipitants. Protocols that utilize organic precipitants for crystallizing antibodies have been described. Yang et al., PNAS, vol. 100, no. 12, pp. 6934-6939 (2003); Kuznetsov et al., J. Crystal Growth, vol. 232, pp. 30-39 (2001); Kuznetsov et al., J. Structural Biology, vol. 131, pp. 108-115 (2000); Harris et al., Immunological Reviews, vol. 163, pp. 35-43 (1998); Harris et al., J. Mol. Biol., vol. 275, pp. 861-872, (1998); and Harris et al., Proteins, vol. 23, pp. 285-89 (1995). Examples of commonly used organic or polymeric precipitants include polyethylene glycol (PEG), isopropanol, Jeffamine® (Huntsman Petrochemical Corp., Salt Lake City, Utah), and (+/−)-2-methyl-2,4-pentanediol (MPD).
As many antibodies are now processed on a large scale for administration to humans, it is desirable to have methods of forming crystals and/or concentrated protein gels on a large scale, especially those that do not include organic or polymeric precipitants. The crystals and/or gels are useful for storage and administration therapeutically.